The warnings may be missed by an awful lot of customers. The United States has 292 million wireless numbers in use, approaching one for every adult and child, according to C.T.I.A.-The Wireless Association, the cellphone industry’s primary trade group. It says that as of June, about a quarter of domestic households were wireless-only.

If health issues arise from ordinary use of this hardware, it would affect not just many customers but also a huge industry. Our voice calls — we chat on our cellphones 2.26 trillion minutes annually, according to the C.T.I.A. — generate $109 billion for the wireless carriers.